Visiting southern Africa as a tourist introduced a Wellington woman to a new environment where she could make an enormous difference to children's lives.

Just three years later Denise Carnihan and her husband Chris have founded a school in a Kenyan slum and it is giving more than 300 children an education.

Ms Carnihan was a casual office administration worker in Wellington and her husband was a self- employed home maintenance man when they were drawn to Africa in 2009 by the discovery of unknown family.

During a commercial tour of southern Africa the Pukerua Bay couple visited some orphanages.

Inspired, Ms Carnihan returned alone to Kenya to volunteer at an orphanage and at a detention centre for teenage boys, where she met Ayub Nasongo, a "fantastic teacher".

"I absolutely loved the whole experience," she said. "It was more than I ever dreamed it would be, so I wanted my husband to experience it, too."

They returned to volunteer again the following year, but when they met Mr Nasongo they found he was working unpaid, because of corruption, Ms Carnihan said.

"After he left I made a random comment to my husband: 'Wouldn't it be cool if we could build a school for 50 kids in a slum and could get Ayub to run it?"'

Ms Carnihan was surprised when her husband agreed.

They invited a friend, Mandy Edmundson of Churton Park, to participate and she was keen.

Ms Edmundson said she had been visiting Nairobi to do some voluntary work.

"Because I went there to do that I had quite a bit of money people had given me to help in the voluntary area."

The school seemed an ideal cause, she said.

"I think we were a bit naive at the beginning. We thought it could be self-funding."

Now that it is clear that it cannot, Ms Edmundson is happy to be in for the long haul, she said.

"I think it is a worthwhile cause."

It was important to the three that the school was fully registered and followed the local curriculum, that all staff were paid and the community was involved where possible.

"It was also important to have an African school, not a European school, so we were directed by Ayub and the local community on the local building way, which meant iron sheets," she said.

"With the help of Ayub, we rented a plot of land in a very large slum called Kangemi on the outskirts of Nairobi and with the help of local people in the community we built a three-room school."

The modest Kia Ora Children's Learning Centre that opened in September 2011, was intended for 50 children, Ms Carnihan said.

"We walked in on the opening morning and the school was packed with 117 kids all wanting to learn. Parents were still coming through the gates with their kids. At that stage we couldn't take any more."

The three returned to New Zealand that November and began fundraising for another three classrooms, which were built two months later.

When Ms Carnihan returned to Nairobi in March, "I arrived at the school to find 300 kids, Ayub the headmaster, seven teachers and a Masai warrior security guard".